The invention relates in general to driveshaft assemblies, such as are commonly found in the drive train systems of most vehicles. In particular, this invention relates to an improved structure for a compound driveshaft assembly that includes an intermediate constant velocity joint and that is relatively simple and inexpensive to manufacture.
Drive train systems are widely used for generating power from a source and for transferring such power from the source to a driven mechanism. Frequently, the source generates rotational power, and such rotational power is transferred from the source to a rotatably driven mechanism. For example, in most land vehicles in use today, an engine/transmission assembly generates rotational power, and such rotational power is transferred from an output shaft of the engine/transmission assembly through a driveshaft assembly to an input shaft of an axle assembly so as to rotatably drive the wheels of the vehicle. To accomplish this, a typical driveshaft assembly includes a hollow cylindrical driveshaft tube having front and rear end fittings, such as a pair of tube yokes, that are respectively secured to the front and rear ends thereof. The front end fitting forms a portion of a front universal joint that connects the output shaft of the engine/transmission assembly to the front end of the driveshaft tube. Similarly, the rear end fitting forms a portion of a rear universal joint that connects the rear end of the driveshaft tube to the input shaft of the axle assembly. The front and rear universal joints provide a rotational driving connection from the output shaft of the engine/transmission assembly through the driveshaft tube to the input shaft of the axle assembly, while accommodating a limited amount of angular misalignment between the rotational axes of these three shafts.
In some vehicles, the distance separating the engine/transmission assembly and the axle assembly is relatively short. For these vehicles, the driveshaft assembly can be formed from a single, relatively long driveshaft tube having the front and rear end fittings respectively secured to the front and rear ends thereof, as described above. In other vehicles, however, the distance separating the engine/transmission assembly and the axle assembly is relatively long, making the use of a single driveshaft tube impractical. For these vehicles, the driveshaft assembly can be formed from first and second separate, relatively short driveshaft sections. In a compound driveshaft assembly such as this, the front end fitting is secured to a front end of the first driveshaft section and forms a portion of the front universal joint, as described above. Similarly, the rear end fitting is secured to a rear end of the second driveshaft section and forms a portion of the rear universal joint, as also described above. An intermediate universal joint is provided for connecting the rear end of the first driveshaft section to the front end of the rear driveshaft section for rotational movement. A compound driveshaft assembly that is composed of two or more separate driveshaft sections usually requires the use of a structure for supporting the intermediate portions thereof for rotation during use, such as a conventional center bearing assembly.
Traditionally, the various universal joints used in both regular and compound driveshaft assemblies have been cardan type universal joints. In a typical cardan type universal joint, each of the end fittings is embodied as a yoke that includes a body portion having a pair of opposed arms extending therefrom. A cross is provided with a central body portion having four cylindrical trunnions extending outwardly therefrom. The trunnions are oriented in a single plane and extend at right angles relative to one another, and a hollow cylindrical bearing cup is mounted on the end of each of the trunnions. Needle bearings or other friction-reducing structures are provided between the outer cylindrical surfaces of the trunnions and the inner cylindrical surfaces of the bearing cups to permit rotational movement of the bearing cups relative to the trunnions during operation of the universal joint. The bearing cups supported on the first opposed pair of the trunnions of the cross are connected to the opposed arms of the first yoke, while the bearing cups supported on the second opposed pair of the trunnions of the cross are connected to the opposed arms of the second yoke.
More recently, however, one or more of the various universal joints used in both regular and compound driveshaft assemblies have been constant velocity type universal joints. A typical constant velocity universal joint includes a cylindrical inner race that is connected to one of the shafts and a hollow cylindrical outer race that is connected to the other of the shafts. The outer surface of the inner race and the inner surface of the outer race have respective pluralities of grooves formed therein. Each groove formed in the outer surface of the inner race is associated with a corresponding groove formed in the inner surface of the outer race. A ball is disposed in each of the associate pairs of grooves. The balls provide a driving connection between the inner and outer races. An annular cage is typically provided between the inner and outer races for retaining the balls in the grooves. The cage is provided with a plurality of circumferentially spaced openings for this purpose.
Although the use of constant velocity joints in both regular and compound driveshaft assemblies has been effective, they have been found to be relatively complex and expensive to manufacture, particularly in the context of a compound driveshaft assembly. Thus, it would be desirable to provide an improved structure for a compound driveshaft assembly that includes an intermediate constant velocity joint and that is relatively simple and inexpensive to manufacture.